I purchased a home in Central New York that was built in 2006. The 2000 sqft basement is 12 courses of block with all but one or two blocks below grade. The blocks have been filled with CoreFoam insulation that has an R value of R-12.25. The basement is unfinished at this time. The walls appear dry, but I do need to run a dehumidifier. There is a french drain around the perimeter that is always dry. There is a sump with a natural drain (i.e. no sump pump).
I want to finish the basement for as a rec room. I have done a fair amount of research, including the Building Science website. I understand that one acceptable method of finishing the walls would be to install 2" of XPS, stud the walls and sheetrock. There are variations, but bottom-line, you need to install the XPS to provide enough insulation (about R-10) to prevent condensation and to allow the moisture to slowly move to the inside of the room. Of coures, you still need a dehumidifier. That's the basics of what I've learned and I don't believe it necessary to rehash the strategy of the Building Science website to ask my question.
The cost for 2"x4'x8' XPS is close to $29 a sheet. Since the CoreFoam filled block walls have an R-12.25 rating, do I need a full 2" of XPS or can I use a thinner sheet? I see it comes in thicknesses as low as 3/8". Would my current block walls already prevent condensation from forming? Do I need the XPS just to slowly release any moisture into the interior? I'm willing to install the XPS, but if 2" is overkill under my circumstances, then I'd like to save some cash. Any thoughts would be appreciated.
I want to finish the basement for as a rec room. I have done a fair amount of research, including the Building Science website. I understand that one acceptable method of finishing the walls would be to install 2" of XPS, stud the walls and sheetrock. There are variations, but bottom-line, you need to install the XPS to provide enough insulation (about R-10) to prevent condensation and to allow the moisture to slowly move to the inside of the room. Of coures, you still need a dehumidifier. That's the basics of what I've learned and I don't believe it necessary to rehash the strategy of the Building Science website to ask my question.
The cost for 2"x4'x8' XPS is close to $29 a sheet. Since the CoreFoam filled block walls have an R-12.25 rating, do I need a full 2" of XPS or can I use a thinner sheet? I see it comes in thicknesses as low as 3/8". Would my current block walls already prevent condensation from forming? Do I need the XPS just to slowly release any moisture into the interior? I'm willing to install the XPS, but if 2" is overkill under my circumstances, then I'd like to save some cash. Any thoughts would be appreciated.